In the context of this specification, a nozzle is basically a device attached to a source of "fluidic" material from which the material is ejected as a stream. In the context of this specification, a fluidic material would include liquids and/or powders. Therefore, according to this definition, a nozzle is a device that dispenses paint from a sprayer, water from a garden hose, or powder from a powder coating gun. Depending on the construction of the nozzle, the stream may be ejected in different forms such as a continuous confined stream (e.g., a fire hose) or as an unconfined mist (e.g., as used for irrigation purposes in greenhouses). The nozzle provides an orifice through which the fluidic material flows from the pressurized area to the surrounding area at ambient pressure. Velocity of the flow depends on the pressure drop through the orifice divided by the resistance of the orifice to the flow of fluidic material. The shorter the orifice, (the distance between the inside and outside of the orifice) the smaller is the resistance and the greater will be the velocity of the stream issuing from the nozzle. If the cross sectional area of the nozzle is small enough and the velocity through the orifice is great enough, then the frictional force exerted on the stream by the sides of the orifice will cause the stream to disperse to a spray or even a mist.
Nozzle technology is generally concerned with--shaping the orifice and controlling the dimensions of the orifice in order to produce a desired pattern and continuity of the stream;
supporting a number of nozzles and/or moving a single nozzle in order to obtain a desired distribution of the stream.
taking precautions to prevent the collection of residues in the orifices which would otherwise cause malfunction of the nozzle.
Various constructions of nozzles have been disclosed for controllably modifying the streams issuing from nozzles. For example, the well known nozzle for a garden hose simply comprises a plug on a stem positioned adjacent to the opening to a channel leading from pressurized water to the ambient region. The position of the plug relative to the opening may be adjusted by turning a screw to which the plug is attached. When the plug is close to the opening, the resultant orifice is very small and the stream of water issues forth as a spray which fans out over a wide area from the nozzle. When the plug is spaced at a distance from the opening, the water issues as a continuous confined stream.
An example of nozzles arranged in series is in drip irrigation where a plurality of nozzles are attached to a single pipeline. In irrigating large areas such as athletic fields, the nozzle assembly is constructed to periodically vary the direction of the stream in order that a few number of nozzles can irrigate a large area.
A nozzle is inherently prone to clogging problems since the orifice is a natural collection point for particulates that ultimately impede the flow of the stream.
The problem is particularly acute in polishing operations where a slurry of liquid lubricant containing a polishing abrasive is sprayed onto a surface as the surface is subject to being polished. If the abrasive includes relatively large particles that jam into the orifice, the orifice eventually becomes clogged to the point where flow is substantially impeded.
A problem that is often encountered in these polishing operations is that the abrasive particles coagulate in quiescent regions of the slurry stream, e.g., in the bottom of a slurry container when the operation is shut down, and these coagulated particles either clog the orifice or, if they escape through the orifice, they scratch the surface being polished. One attempted solution is to continuously circulate the slurry even when the operation is not in use.
In applications where separation of a fluidic material such as a powder into one component containing particles greater than a critical size from particles smaller than the critical size, a preparatory step such as filtering through a sieve may be resorted to before sending the fluidic material through the nozzle. Of course, the problem with sieving and filtering operations is that the openings in the sieve or filter become clogged so that the filtering characteristics of the sieve or filter change with time and periodic backflushing in order to clear the clogged holes is required.
Sprays are also used extensively in rinsing operations. A frequent requirement in these applications is that the spray be applied in a fan shaped pattern. This shape of pattern requires emmision through a slot wherein the dimensions of the slot control the overall shape of the spray pattern. An array of more than one nozzle is also used to obtain a desired shape of spray pattern.
An example of a disclosure to control a spray pattern is U.S. Pat. No. 4,905,906 which discloses a spring loaded piston operating against a trigger to position a rod in relation to the opening in a nozzle.
U.S. Pat. No. 4,904,505 discloses a header assembly of nozzles, "sized to produce a mist" in order to apply a lubricant to the surface of a roll of sheet metal.
U.S. Pat. No. 4,895,413 discloses a nozzle holder that is constructed to control flow of liquid TO THE NOZZLE in a cutter roller operation.
A system of watering lawns is well known wherein the hose has a line of small holes in the holes. The size of the holes is fixed so that the size of the spray depends on the pressure of water in the hose. With this system, the rate of flow through each orifice is less than from its neighboring orifice closer to the source.